Nutrients are the mediators of metabolism, thus their cytoplasmic levels need to be precisely controlled. Previous study by Emr and colleagues revealed that a yeast Lys transporter present on the vacuole (the yeast equivalent of the lysosome) membrane is ubiquitylated and degraded when Lys levels are low. Now, they provide evidence that this mechanism is more broadly utilized and also that vacuolar Zn2+ transporters are regulated by ubiquitylation in response to Zn2+ levels. In this case, however, a separate protein complex (known as the Dsc complex), together with a distinct, transmembrane ubiquitin ligase Tul1, was primarily responsible. These results demonstrate that cells can react to changes in nutrient availability by specific, ubiquitin-mediated degradation of vacuolar transporters, thus influencing the shuttling of nutrients between the cytoplasm and the lysosomal compartment.
References
Li, M. et al. Membrane-anchored ubiquitin ligase complex is required for the turnover of lysosomal membrane proteins. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201505062 (2015)
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Strzyz, P. Maintenance of nutrient homeostasis. Nat Rev Mol Cell Biol 16, 703 (2015). https://doi.org/10.1038/nrm4095
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DOI: https://doi.org/10.1038/nrm4095